Process of forming a paving material.



- MICHAEL A. POIPKESS,

SAS CITY, MISSOURI, ASS IGNOR .TO BITUMINIZED ROAD COMPANY, ACOBPORATION'OF ARIZONA.-

IPROCESS 0F FORMING A PAVING MATERIAL.

LQQUMBMI".

No Drawing.

To all whom it may concern:

Be it known-that T, MICHAEL A. PorKEss, a citizen of the United States,residingat Kansas City, in the county of Jackson and State of Missouri,have invented new and" useful Improvements in Processes of EOE-m ing aPaving Material, of which the follow: ing is a specification. Y 5

he present invention relates to the production of a substance, suitablefor paving purposes and the like, the main ingredient of which is amaterial which has heretofore been considered quite unsuitable for suchpurposes. a

There exist, in most localities, deposits of sand, gravel and earthymaterial, .or stone in a more or less decomposed or disintegrated state,sometimes called rotten stone or dirty sand and gravel. Such material,in its natural state, cannot be easily mixed with a bituminous binder soas to form a durable product. The reason ap-' pears to be that the fineor earthy material forms a coating or shell around and adherent to thelarger stony particles, which coating or shell prevents the bitumen'fromcoming into contact with said stony particles and, therefore, fromcementing them together. v 7

Consequently, such deposits have never come into practical commercialuse, as an ingredient of paving material, and, therefore, at the presentday it is always required that the mineral aggregate for asphaltpavements shall consist of clean, hard, sharp particles of graded sizes.Dirty sandor gravel is not permitted.

Where attempts have been made to use deposits, such as described-above,the plasticity and colloidal qualities of the earthy material weredestroyed, owing to the high temperatures used, whereby it was caused tofiocculate or form lumps which absorbed Water but not the bituminousbinder.

, Specification of Letters Patent. v Patented Mar. 2?, 11ml '2'.Application filed April 1t),

1916', Serial in. 90,244.

results as possible, it is necessary that the mineral aggregate bepractically free from earthy material and graded so that there is .aninterlocking of theseparticles. The stabilityof the pavement'is governedby this ...interlocking, and, for that reason round particles are notsatisfactory,-but, as above stated, clean, hard, sharp and" irregularparticles are demanded, the idea in this type of I pavement being-tohave the. aggregate support the trafic by. the stony particles rest,-ing on each other and with the bitumen merely cementing said particlestogether.

In actual construction'work where large quantities of different sizedmaterials are us ed, the interlocking of the different sizes of materialis imperfectly attained on ac- Count of the fact that the largeparticles separate .more or less from the fine particles in the-roadmaking operation and the difl'erent sizes tend to segregate into. clumpsin the mixing thereof, which prevents the interlocking and close comacting action.

tion of-holes; it also causes creeping, which makes the pavementunevenand wavy.

Also, the gradual. crushing of the minerali aggregate in asphalticpavements, as ordinarily constructed, produces mineral parti-f cleswhich are not coated with bitumen, thus destroying the cementation andallowing the pavement to erode and wear into holes.

When a sheet asphalt or asphaltic concrete pavement becomes hot, thebitumen be:

comes thinly liquid and ceases to act as a cement and its only valuethen is that it par-v tially water-proofs the mineral aggregate,

to the extent that it fills part of the large voids with .too muchbitumen and the small voids with too little. As a result, all of theload on the surface must be borne' by the' mineral aggregate, whichtransfers the load directly downward to the base, and on account of thelack of tensile strength in the mineral aggregate which' -constitutesthe wearingzsurface, a rigid base of concrete or the like is considerednecessary.

Heretofore, in making bituminous pavements,composed of a mineralaggregate and asphalt, the high temperatures used in heating theaggregate preparatory to mixing it with the asphalt, which wasnecessarily a hard asphalt of low penetration, made the mixture too hotand tended to coke the latter asphalt, which therefore, lost most of'its cementing property, causing the pavement to disintegrate and theformation of holes therein.

The present invention is a development of that covered by my Patent No.1,008,433, and was conceived or discovered in the experimental use ofthe machine which is disclosed in myapplication of April 4, 1914, SerialNo. 829,549, the object being to meet the demand for a cheaper kind of,material.

Said machine is designed to deliver fine dry dust produced by drying,disintegrating and sifting ordinary earthy material; and it comprises aslowly rotating drum, within which is a rapidly revolving pulverizer,while between the latter and said drum is a screen cylinder, attached tothe latter, the purpose of said cylinder being to separate out the dustfrom the larger particles as fast as it is formed.

While this machine was designed for the treatment of earthy material,substantially free fromsand and gravel, such as that used 'in practisingthe process of my said patent,

tests were made with earthy material such as described above, containingmore or less gravel, dirty sand, disintegrated rock and the like.Naturally, the larger particles were not disintegrated into dust and didnot pass through the screen but were delivered out at the rear endthereof, and were then mixed with the dust and binder. I then discoveredthat by the action of the pulverizer and the screen andthe heat, thesaid solid stony particles though not disintegrated had been thoroughlycleaned from all adhering dirt and, indeed, were fractured and polished,and that, in that condition, the mixture of binder and earth wouldadhere to and coat them, and that the product, consisting of suchcleaned stony particles, and of the combined earthy dust and binder,after being compacted, either to form a pavement in situ or into blocks,was practically as coherent and possessed almost as much tensilestrength as my previous product made from earthy material substantiallyfree from sand, gravel and stone.

The present process and the resulting productpresent several advantages,one of which is the fact that material can be used which is found nearlyeverywhere and has heretofore had no commercial value as an ingredientof a paving or the like; another is that the gravel and stony particlesact as a filler, thereby reducing the amount of bituminous binderrequired, and reducing the cost, where paving specifications call for acheaper grade of pavement. I

Any type of pulverizing machine can be used for the purposes of thepresent invention provided it be run in such a way that the harderbodies or particles are not materially disintegrated but are merelycleaned or cleaned and fractured.

In the present invention the decomposed and disintegrated earthymaterial, mixed with the bitumen, completely fills the voids and acts asa cushion between the clean and fractured solid particles andconstitutes itself a malleable wearing material, which that describedherein, because it rapidly fractures and wears away under the conditionsof modern trafl'ic, which demand a different kind of supporting surfacefrom that which was fairly satisfactory under old traffic conditions.

I have also found that, when the hard particles crack and grind away, orcome out of the surface of my pavement, this wear resisting substance,consisting of bitumen and earthy material will actually iron out andfill the voids left by the stony particles, so that, eventually, thewearing surface comes to consist. entirely of the wear-resisting binder,which is not the case with the binders heretofore used in otherbituminous pavements. The sand and gravel particles act more as a fillerthan as a wearing aggregate, thereby reducing, as above stated, theamount of bitumen required. Furthermore, the present process requires nograding or sizing of the mineral aggregate because the stability of thepavement does not depend upon the interlocking of the particles of stonymaterial.

While the process is very advantageously carried out by the machine ofmy said application, it does not necessarily require the use of that orany other particular machine, since obviously various means may beemployed to clean the gravel, etc., or free it from adhering earthymaterial before it is mixed with the binder and the fine material.

While the use of heat seems to be' advantageous it is not essential inall cases, and particularly where if a natural liquid asphalt is used.

Whereas, in some cases, it is better to with, it is not essential to thesuccessful op-,

eration of my process.

It is immaterial, as faras the present process is concerned, what therelative percentages of stony and earthy or soft material are, orwhether the particles of stony material are sharp or rounded. Theresulting product varies in its composition according to the percentageof fine dust, from a pave: ment similar to an ordinary sheet asphalt tothat now clai ed in my application, Serial No. 92,704 April 21, 1916.

In cases Wherefthe natural earth does not contain the amount of sand,gravel or crushed rock required or desired, it is obvious that more canbe added.

What I claim is:

1. The process of preparing a sulbstance suitable for paving andsurfacing purposes, which consists in subjecting dirty gravel and sandto a disintegrating, cleaning and polishing treatment and intimatelymixing the resulting material with a bituminous binder.

2. The process of producing a homogeneous wear resisting substance forpaving or other surfacing purposes, which consists in simultaneouslypulverizing friable earthy material and cleaning hard stony particlesand mixing the same with a bituminous binder.

3. The process of forming a paving material, which consists insubjecting, natural mixtures of stony and earthy material to adisintegrating action which partially pul verizes and partially cleansand fractures the same, and thoroughly mixing a bituminous binder withthe resulting material.

4. The process of producing a paving material, which consists in takingnatural mixtures of stony and earthy material, subjecting them to atreatment whereby the softer or earthy ingredients are reduced to dustand the harder stony ingredients are freed or cleaned from the adheringsofter mate rial, and impregnating and mixing the resuiting materialwith asphalt.

5. The process of producing a homogeneous wear resisting substance forpaving purposes and the like, which consists in impregnatingdisintegrated earthy material with bituminous binder, incorporating amineral aggregate with similar binder, and mixing both materialstogether.

6. The process of producing a homogeneouswear-resisting substance whichcomprises comminuting-earthy material to a high degree of fineness,thoroughly impregnating the comminuted material with a bituminousbinder, cleaning a hard mineral aggregate and incorporating it with abituminous binder and thoroughly mixing the resulting materials.

7. The process of preparing a substance suitable for paving andsurfacing purposes, which consists in subjecting natural mix tures ofstony or rocky and earthy matter,

' to a mechanical treatment by which the friable and finer material iscomminuted and separated out from the coarse and solid material, and thelatter is cleaned and polished, and intimately mixing and impregnatingboth said materials with a bituminous binder.

8. The process of preparing a substance suitable for paving andsurfacing purposes, which consists in subjecting natural mixtures ofstony or rocky and earthy matter to the action of heat and of mechanicalmeans, whereby the friable and finer material is comminuted andseparated from the remainder, and mixing both the comminuted and theremaining material together with a bituminous binder.

9. The process of preparing a substance suitable for paving andsurfacing purposes, which consists in subjecting natural mixtures ofstony or rocky and earthy 'matter to a separating treatment whereby thelarger solid particles of mineral matter are cleaned and separated fromthe friable and finer matter, impregnating the latter with a bituminousbinder, and mixing it with said larger particles.

10. The process of preparing a substance suitable for paving andsurfacing purposes, which consists in subjecting mixtures of solid-andfriable mineral matter to a treatment whereby the friable matter iscomminuted and the solid matter is cleaned, polished and fractured, andmixing the comminuted and cleaned particles with a bituminous binder,whereby, when the product is compacted, it will possess unusual tensilestrength, be malleable and yet resilient and possess great durability.

11. The process of preparing a substance suitable for paving andsurfacing purposes, which consists in subjecting natural mixtures ofstony or rocky and earthy matter to a separating treatment whereby thelarger solid particles of mineral matter are cleaned and separated fromthe friable and finer matter, impregnating the latter with a bituminousbinder and stirring into said mixture said larger cleaned particles.

12. The process of forming a paving material, which consists insubjecting mixtures of hard and soft stones and earthy material to adisintegrating action which pulverizes the soft stones, disintegratesthe earthy material and fractures and cleans the hard stones, and mixingthe resulting material with a bituminous binder.

13. The process of producing a homogeneous wear-resisting substanceadapted for pavement and other purposes which com-v comminuting soil,loam or clay to a high degree of fineness, thoroughly impregnating thecomminuted material with a bituminous binder, the proportion of suchcomminuted soil, loam or clay relative to such bituminous binder beingsuch as to give a malleable, coherent wearing material capable ofwithstanding traflic, incorporating mto the mixture a clean hard mineralaggregate, and thoroughly mixing the re- 10 my hand.

MICHAEL A. POPKESS.

